Day 0 Support: GPT-5.6 (Sol, Terra, Luna)

LiteLLM now supports the GPT-5.6 family. Route traffic to OpenAI's newest frontier models through the LiteLLM AI Gateway with no code changes.

GPT-5.6 introduces a new naming system where the number identifies the generation and the tier name identifies a durable capability level. gpt-5.6-sol is the flagship for complex reasoning and agentic workloads, gpt-5.6-terra is a balanced model for everyday work with performance competitive with GPT-5.5 at roughly half the cost, and gpt-5.6-luna is the fastest and most affordable tier. Per OpenAI, the family sets a new state of the art on agentic coding (Terminal-Bench 2.1) with broad gains in long-horizon biology and cybersecurity workflows. GPT-5.6 also adds a new max reasoning effort for the deepest single-agent thinking and an ultra mode that coordinates subagents on the most complex tasks.

Living post

This post is updated as GPT-5.6 support expands. Azure OpenAI support for the GPT-5.6 models is coming soon; today the post covers OpenAI direct. Check back soon for Azure availability and pricing details.

note

No Docker image upgrade needed. GPT-5.6 routes through the existing OpenAIGPT5Config in LiteLLM (the version classifier already matches gpt-5.4 and newer), so any recent version works out of the box.

For cost tracking, hit the Reload Model Cost Map button in the Admin UI (or POST /reload/model_cost_map) to pull the latest pricing from GitHub. This feature is available on v1.76.0 and above.

Usage

LiteLLM Proxy

1. Setup config.yaml

model_list:
  - model_name: gpt-5.6-sol
    litellm_params:
      model: openai/gpt-5.6-sol
      api_key: os.environ/OPENAI_API_KEY
  - model_name: gpt-5.6-terra
    litellm_params:
      model: openai/gpt-5.6-terra
      api_key: os.environ/OPENAI_API_KEY
  - model_name: gpt-5.6-luna
    litellm_params:
      model: openai/gpt-5.6-luna
      api_key: os.environ/OPENAI_API_KEY

2. Start the proxy

docker run -d \
  -p 4000:4000 \
  -e OPENAI_API_KEY=$OPENAI_API_KEY \
  -v $(pwd)/config.yaml:/app/config.yaml \
  ghcr.io/berriai/litellm:v1.91.1 \
  --config /app/config.yaml

3. Test it

curl -X POST "http://0.0.0.0:4000/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $LITELLM_KEY" \
  -d '{
    "model": "gpt-5.6-sol",
    "messages": [
      {"role": "user", "content": "Write a Python function to check if a number is prime."}
    ]
  }'

LiteLLM Python SDK

from litellm import completion

response = completion(
    model="openai/gpt-5.6-sol",
    messages=[
        {"role": "user", "content": "Write a Python function to check if a number is prime."}
    ],
)

print(response.choices[0].message.content)

# gpt-5.6-terra for balanced, cost-efficient everyday work
response = completion(
    model="openai/gpt-5.6-terra",
    messages=[
        {"role": "user", "content": "Summarize the key ideas in this design doc."}
    ],
)

print(response.choices[0].message.content)

# gpt-5.6-luna for the fastest, lowest-cost tier
response = completion(
    model="openai/gpt-5.6-luna",
    messages=[
        {"role": "user", "content": "Classify this ticket as bug, feature, or question."}
    ],
)

print(response.choices[0].message.content)

Responses API

For agentic and multi-turn workflows, use /v1/responses to preserve reasoning state and output item metadata across turns.

curl -X POST "http://0.0.0.0:4000/v1/responses" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $LITELLM_KEY" \
  -d '{
    "model": "gpt-5.6-sol",
    "input": "Plan and write a Python script that scrapes a webpage and summarizes it."
  }'

Pricing

Prices are per 1M tokens (USD), shown as short context (≤272K tokens) / long context (>272K tokens).

Model	Input	Cached input	Cache write	Output
gpt-5.6-sol	$5.00 / $10.00	$0.50 / $1.00	$6.25 / $12.50	$30.00 / $45.00
gpt-5.6-terra	$2.50 / $5.00	$0.25 / $0.50	$3.125 / $6.25	$15.00 / $22.50
gpt-5.6-luna	$1.00 / $2.00	$0.10 / $0.20	$1.25 / $2.50	$6.00 / $9.00

Notes

• For cost tracking on the GPT-5.6 models, hit the Reload Model Cost Map button in the Admin UI (or POST /reload/model_cost_map). Works on any LiteLLM version v1.76.0 or newer, with no container restart or image upgrade required.
• GPT-5.6 supports reasoning, function calling, parallel tool calls, vision (image input), prompt caching, web search, and structured output; see the OpenAI provider docs for advanced usage.
• The GPT-5.6 family launched in limited preview and OpenAI is expanding availability through the API and Codex; check your OpenAI account for model access.